std::priority_queue<T,Container,Compare>::priority_queue
From cppreference.com
< cpp | container | priority queue
priority_queue() : priority_queue(Compare(), Container()) { } |
(1) | (since C++11) |
explicit priority_queue(const Compare& compare) : priority_queue(compare, Container()) { } |
(2) | (since C++11) |
(3) | ||
explicit priority_queue( const Compare& compare = Compare(), const Container& cont = Container() ); |
(until C++11) | |
priority_queue( const Compare& compare, const Container& cont ); |
(since C++11) | |
priority_queue( const Compare& compare, Container&& cont ); |
(4) | (since C++11) |
priority_queue( const priority_queue& other ); |
(5) | |
priority_queue( priority_queue&& other ); |
(6) | (since C++11) |
template< class Alloc > explicit priority_queue( const Alloc& alloc ); |
(7) | (since C++11) |
template< class Alloc > priority_queue( const Compare& compare, const Alloc& alloc ); |
(8) | (since C++11) |
template< class Alloc > priority_queue( const Compare& compare, const Container& cont, |
(9) | (since C++11) |
template< class Alloc > priority_queue( const Compare& compare, Container&& cont, |
(10) | (since C++11) |
template< class Alloc > priority_queue( const priority_queue& other, const Alloc& alloc ); |
(11) | (since C++11) |
template< class Alloc > priority_queue( priority_queue&& other, const Alloc& alloc ); |
(12) | (since C++11) |
template< class InputIt > priority_queue( InputIt first, InputIt last, |
(13) | (since C++11) |
template< class InputIt > priority_queue( InputIt first, InputIt last, |
(14) | (since C++11) |
Constructs new underlying container of the container adaptor from a variety of data sources.
1) Default constructor. Value-initializes the comparator and the underlying container.
2) Copy-constructs the comparison functor
comp
with the contents of compare
. Value-initializes the underlying container c
.3) Copy-constructs the underlying container
c
with the contents of cont
. Copy-constructs the comparison functor comp
with the contents of compare
. Calls std::make_heap(c.begin(), c.end(), comp). This is also the default constructor. (until C++11)4) Move-constructs the underlying container
c
with std::move(cont). Copy-constructs the comparison functor comp
with the contents of compare
. Calls std::make_heap(c.begin(), c.end(), comp). 5) Copy constructor. The adaptor is copy-constructed with the contents of other.c. The comparison functor is constructed with std::move(other.comp). (implicitly declared)
6) Move constructor. The adaptor is constructed with std::move(other.c).The comparison functor is constructed with std::move(other.comp). (implicitly declared)
7-12) The following constructors are only defined if std::uses_allocator<container_type, Alloc>::value == true, that is, if the underlying container is an allocator-aware container (true for all standard library containers).
7) Constructs the underlying container using
alloc
as allocator. Effectively calls c(alloc). comp
is value-initialized.8) Constructs the underlying container using
alloc
as allocator. Effectively calls c(alloc). Copy-constructs comp
from compare
.9) Constructs the underlying container with the contents of
cont
and using alloc
as allocator, as if by c(cont, alloc). Copy-constructs comp
from compare
. Then calls std::make_heap(c.begin(), c.end(), comp). 10) Constructs the underlying container with the contents of
cont
using move semantics while using alloc
as allocator, as if by c(std::move(cont), alloc). Copy-constructs comp
from compare
. Then calls std::make_heap(c.begin(), c.end(), comp). 11) Constructs the adaptor with the contents of
other.c
and using alloc
as allocator. Effectively calls c(other.c, alloc). Copy-constructs comp
from other.comp
.12) Constructs the adaptor with the contents of
other
using move semantics while utilising alloc
as allocator. Effectively calls c(std::move(other.c), alloc). Move-constructs comp
from other.comp
.13) Copy-constructs
c
from cont
and comp
from compare
. Then calls c.insert(c.end(), first, last);, and then calls std::make_heap(c.begin(), c.end(), comp);.14) Move-constructs
c
from std::move(cont)
and comp
from std::move(compare)
. Then calls c.insert(c.end(), first, last);, and then calls std::make_heap(c.begin(), c.end(), comp);.Parameters
alloc | - | allocator to use for all memory allocations of the underlying container |
other | - | another container adaptor to be used as source to initialize the underlying container |
cont | - | container to be used as source to initialize the underlying container |
compare | - | the comparison function object to initialize the underlying comparison functor |
first, last | - | range of elements to initialize with |
Type requirements | ||
-Alloc must meet the requirements of Allocator.
| ||
-Container must meet the requirements of Container. The constructors (5-10) are only defined if Container meets the requirements of AllocatorAwareContainer
| ||
-InputIt must meet the requirements of LegacyInputIterator.
|
Complexity
1-2) Constant.
3,5) O(N) comparisons, where N is cont.size().
Additionally, O(N) calls to the constructor of
value_type
, where N is cont.size().4) O(N) comparisons, where N is cont.size().
6-8) Constant.
9) O(N) comparisons, where N is cont.size().
Additionally, O(N) calls to the constructor of
value_type
, where N is cont.size().10) O(N) comparisons, where N is cont.size().
11) Linear in size of
other
.12) Constant.
Additionally, O(N) calls to the constructor of
value_type
, where N is cont.size().Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR | Applied to | Behavior as published | Correct behavior |
---|---|---|---|
P0935R0 | C++11 | default constructor and constructor (4) were explicit | made implicit |
Example
Run this code
#include <queue> #include <vector> #include <iostream> #include <functional> int main() { std::priority_queue<int> c1; c1.push(5); std::cout << c1.size() << '\n'; std::priority_queue<int> c2(c1); std::cout << c2.size() << '\n'; std::vector<int> vec={3, 1, 4, 1, 5}; std::priority_queue<int> c3(std::less<int>(), vec); std::cout << c3.size() << '\n'; }
Output:
1 1 5
Example With Custom Comparator
Run this code
#include <iostream> #include <queue> #include <vector> #include <utility> using my_pair_t = std::pair<size_t,bool>; using my_container_t = std::vector<my_pair_t>; int main() { auto my_comp = [](const my_pair_t& e1, const my_pair_t& e2) { return e1.first > e2.first; }; std::priority_queue<my_pair_t, my_container_t, decltype(my_comp)> queue(my_comp); queue.push(std::make_pair(5, true)); queue.push(std::make_pair(3, false)); queue.push(std::make_pair(7, true)); std::cout << std::boolalpha; while(!queue.empty()) { const auto& p = queue.top(); std::cout << p.first << " " << p.second << "\n"; queue.pop(); } }
Output:
3 false 5 true 7 true
See also
assigns values to the container adaptor (public member function) |